1. Field of the Invention
The present invention relates to an electroluminescent device and a method for fabricating the same, and in particular relates to an active matrix organic electroluminescent device with various channel thickness and fabrication method thereof.
2. Description of the Related Art
Recently, with the development and wide application of electronic products such as mobile phones, PDAs, and notebook computers, there has been increasing demand for flat display devices that consume less power and occupy less space. Organic electroluminescent devices are self-emitting and highly luminous, with wider viewing angle, faster response speed, and a simple fabrication process, making them an industry display of choice.
Organic light-emitting diodes (OLED) utilize an organic electroluminescent layer. The trend in organic electroluminescent display technology is for higher luminescent efficiency and longer lifetime. As a result, an active matrix organic electroluminescent device with thin film transistors has been developed to solve the aforementioned problems. The active matrix organic electroluminescent device has panel luminescence with thin and lightweight characteristics, spontaneous luminescence with high luminescent efficiency and low driving voltage, and advantages of increased viewing angle, high contrast, high-response speed, flexibility and full color. As the need for larger display devices with higher resolution grows, active matrix organic electroluminescent devices are poised to achieve a major market trend.
As to conventional formation of electroluminescent devices, semiconductor layers are mainly formed at a uniform thickness due to simplicity of process. That is, semiconductor layers of peripheral driving circuits of a panel, or of TFTs and storage capacitors in a sub-pixel may be formed simultaneously to a desired thickness. For example, U.S. Pat. No. 6,337,232 discloses a fabrication method of a crystalline silicon thin film semiconductor with a thin channel region. In the presented electroluminescent device, a semiconductor film including silicon is formed. After crystallization of the semiconductor film followed by patterning of the crystallized semiconductor film, a maker part and an insular part are formed simultaneously. Specifically, a part of the semiconductor film to become a channel formation region is thinned to a thickness of 300 angstroms or less.
Conventional electroluminescent devices, however suffer from problems such as the so-called “mura” effect induced by various electric field effect mobility of driving TFTs among sub-pixels. Accordingly, an electroluminescent device capable of solving the aforementioned problems is desirable.